The invention relates to a feeding or matching circuit for feeding signal circuits conducted via a multi-pin plug-in connection of a freely programmable control unit or of a control and instrumentation system comprising at least one electronic module which carries a part of the plug-in connection, or for matching the signal circuits to the inputs or outputs of this module.
The control engineering or instrumentation engineering tasks occurring in practice are of the most manifold nature and, as a rule, are different in each case of application. As far as is permitted at all by the variety of tasks to be solved, it is attempted to build up the systems as far as possible from standardized elements to minimise costs. However, compromises cannot be avoided A typical interface at which such compromises are required is, for example, the connection of the transmitters and actuators integrated into the process to inputs or outputs of electronic module in the control units or substations of the control and instrumentation systems. The problem occurring here lies, on the one hand, in the differently high signal amplitudes of the transmitters. On the other hand, supply sources must frequently be provided in the connecting circuits, especially of the actuators, which, with respect to their power capacity or their voltage or current level, resectively, cannot or not easily be integrated into the electronics of the electronic modules. Today, the electronic modules are frequently designed without consideration of the various signal amplitudes of the transmitters and without integrated supply for the transmitters and actuators. It is then left to the system constructor to match the signal amplitudes of the transmitters in each individual case to the inputs of the electronic modules, for example by means of load or shunt resistors, and to loop the connecting lines of the actuators and, as far as necessary, of the transmitters, via suitable supply voltage or supply current sources. For this purpose, the connecting lines of the elements mentioned are normally conducted to terminal strips which are arranged somewhere, for example in the switching cabinets containing the electronic modules or several such modules in module racks. From the terminal strips, the connection lines lead to multi-pin connectors which are plugged onto the modules, frequently at their front. The measures mentioned are very elaborate and form a not inconsiderable cost factor in the planning and creation of the control unit and of the control and instrumentation system, respectively.
The invention characterized in the claims achieves the object of achieving rationalization in this case.
The advantages achieved by the invention can be essentially seen in the following points:
for the system constructor, the elaborate loopings of the connecting lines of the transmitter or actuators via terminal strips are no longer necessary, which results in immediate cost savings in the planning of the control unit and of the control and instrumentation system, in its documentation and in its creation;
the electronic modules can be inexpensively developed and constructed independently of the requirements of the particular system; input circuit variants are no longer necessary; modules can be simply exchanged for each other;
the process-dependent functions are cleanly separated from the functions of the modules in the control units or substations;
all inputs and outputs at the modules can generally be of two-pin construction; if a 1 1/2 pin connection is required, this can be achieved by appropriate construction of the intermediate connector;
checking of command outputs of the electronic modules is facilitated; this is because the process-side parts of the modules are still fed after the multi-pin connector has been pulled off without the intermediate connector;
a relay which is common to several signal channels of a module, for example a so-called GO relay, can be arranged outside the module and can be simply connected by means of the intermediate connector;
the solution according to the invention meets EMC requirements (EMC=electromagnetic compatibility);
the intermediate connector can also be optionally omitted, it remains possible to plug the multi-pin connector directly onto the modules;
if the intermediate connector is forgotten, no damage is produced since the supply is then missing;
if, in the case of analog inputs, the intermediate connector is pulled off together with the multi-pin connector but remains plugged onto it, the process is not influenced; this is why modules can be exchanged without influencing the process.